/usr/include/libyelp/ is in libyelp-dev 3.26.0-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libyelp/yelp-bookmarks.h
/usr/include/libyelp/yelp-docbook-document.h
/usr/include/libyelp/yelp-document.h
/usr/include/libyelp/yelp-help-list.h
/usr/include/libyelp/yelp-info-document.h
/usr/include/libyelp/yelp-mallard-document.h
/usr/include/libyelp/yelp-man-document.h
/usr/include/libyelp/yelp-search-entry.h
/usr/include/libyelp/yelp-settings.h
/usr/include/libyelp/yelp-simple-document.h
/usr/include/libyelp/yelp-sqlite-storage.h
/usr/include/libyelp/yelp-storage.h
/usr/include/libyelp/yelp-transform.h
/usr/include/libyelp/yelp-types.h
/usr/include/libyelp/yelp-uri-builder.h
/usr/include/libyelp/yelp-uri.h
/usr/include/libyelp/yelp-view.h